Typically, inorganic materials such as talc, mica, etc. are used as inorganic fillers to improve mechanical properties of polyolefin resins. Conventionally, the incorporation of such inorganic materials into polyolefin resins has been performed by mechanical means. However, the mechanical incorporation frequently results in poor dispersions in which particles of the inorganic materials form multi-layered aggregates because they are incompatible with polyolefin matrixes.
Various attempts have been made, so far, to disperse inorganic layered materials as nano-sized unit layers in polymer matrixes. For example, Journal of Appl. Polym. Scien., vol. 55, pp. 119-123(1995) discloses a polyamide exfoliation type nanocomposite prepared by using 12-aminolauric acid-treated silicate.
Further, Japanese Patent Publication No. Hei. 10-182892 discloses a method for dispersing a layered clay mineral in an olefin-based resinous matrix, the method comprising the steps of: organizing the layered clay mineral; broadening interlayer space of the organic layered clay mineral through the intercalation of a polyolefinic oligomer with functional groups thereinto; and mixing the resulting composite material with the olefin-based resinous matrix.
The radical polymerization of a monomer in the presence of a layered silicate clay mineral is another approach to obtain nanocomposite. However, the polymerization via catalytic mechanism of a Ziegler-Narta or metallocene catalyst cannot be accomplished in the presence of the layered silicate clay mineral due to hydrophilicity of the mineral.